This invention relates to reciprocating plate extractors useful for liquid extraction processes. More particularly, it relates to improvements in reciprocating plate extractors whereby coalescing surfaces are located in the vicinity of the plate stacks in the extractor thereby enhancing the coalescence rate of emulsion droplets which otherwise limit the capacity of the extractor.
Solvent extraction processes are well established techniques in the petroleum, pharmaceutical and chemical industries. Indeed, various types of mechanical agitation have been used in liquid-liquid extractors in an attempt to improve the mass transfer efficiency of such extractors. For example, pulsating energy is one technique that has been employed for obtaining a high rate of mass transfer in a liquid-liquid extractor. More recently, reciprocating plate extractors have been employed to introduce mechanical agitation because of their energy efficiency.
As is known, the flow limiting phenomena in reciprocating extractors results from a build up of droplets, for example, the formation of an emulsion in certain zones between the plates in the extractor. These emulsion droplets eventually progress to the wrong end of the column and in such instances the extractor is said to be flooded. In general, to avoid flooding the mixing energy is reduced, for example, by altering the plate spacing or by altering the amplitude or frequency of plate motion. Unfortunately a reduction in mixing energy results in a reduction in efficiency of the extractor.
Therefore, there remains a need for reciprocating plate extractors which are less prone to flooding and which have greater flow capacity than is presently achieved with reciprocating plate extractors.